Electrets used in measuring rocket exhaust effluents from a space shuttle model

The purpose of this experimental research was to investigate the use of electrets as a measuring device to measure the hydrogen chloride concentrations of rocket exhaust effluents. The word electret was derived by Heaveside (1892) to describe a permanently polarized dielectric, which is the electrical equivalent of a permanent magnet. A Japanese physicist, Eguchi, prepared the first electret in 1919 from carnauba wax (Eguchi, 1919). In assessing the effectiveness of electrets, comparisons were made with hydrogen chloride measuring devices from chamber and field tests and computed results from the NASA/MSFC multilayer diffusion model. The results show that electrets have multi-pollutant measuring capabilities, simplicity of deployment and speed of assessment. Electrets are desirable because of their small size, light weight, long life and low cost of manufacturing.